1. Field of the Invention
The present invention relates to a reading or writing method and apparatus thereof, and more particularly to a method and an apparatus for reading or writing data by driving a reading/writing head, for example, for use in a serial type of facsimile system.
2. Description of the Prior Art
With a serial-type facsimile apparatus, a movable unit serving as a reading/writing head has a unidimensional solid-state image sensor and a heating element for thermal recording which are arranged according to the direction of transport of documents and recording paper. The movable unit performs a reading or writing operation while traveling in a direction perpendicular to the transport direction (see, for example, U.S. Pat. No. 4,564,847 and Unexamined Japanese Patent Publication No. SHO-59-228462).
Accordingly, the serial-type facsimile apparatus has the advantage of being inexpensive to manufacture since there is no need to use expensive electronic parts such as a line sensor extending over the entire width of documents and a heating element extending over the entire width of the recording paper.
However, the movable unit, which is mechanically driven, gives off mechanical noise. Especially in a direction opposite to the reading or writing direction, the movable unit is driven at a high speed, so that mechanical noise during travel and impact noise upon stopping are considered to be a nuisance.
On the recommendation of CCITT (The International Telegraph and Telephone Consultative Committee), a limitation has been imposed on the communication time per line of the facsimile system, whereby the scanning time per stroke of the movable unit is limited. Accordingly, during the return travel (without reading or writing), the movable unit is driven at a particular speed depending on the maximum size of documents being used.
FIG. 4 is a diagram showing the relationship between the speed of travel of the movable unit and time of the reading operation of a conventional facsimile apparatus.
The speed of the movable unit for a document of large size is indicated in the phantom line. For this document, the movable unit starts to travel from a reference position at the start of a period T5, reads the document while traveling over the period T5 and stops on traveling the dimension of the document. The unit is thereafter returned to the reference position over a period of T8.
The speed of the movable unit for a document of small size is represented by a solid line. The unit starts to travel from the reference position with the start of a period T6, reads the document while traveling over the period T6 and stops upon traveling the dimension of the document. The unit thereafter returns to the reference position over a period of T7. When returning to the reference position, the unit travels at a particular speed regardless of the size of documents.
Conventional serial-type facsimile apparatus are generally adapted for use with documents ranging in width from A5 size (148 mm) to A3 size (297 mm). While the documents actually used have varying sizes, documents of maximum size are used rather infrequently. However, even if documents of small size are used, the head is returned at a particular high speed at all times as already stated, consequently producing the same noise as when documents of maximum size are processed.